This invention relates to flat panel displays and, more particularly, to non-light-emitting flat panel displays.
Flat panel displays have received considerable interest as the demand for ultra-light weight, low power miniature displays has increased for both character and graphic output. However, while conventional CRT displays are bulky, no current flat panel technologies can provide the picture quality and brightness, reliability, durability, and ease of manufacture of the CRT. Some of the best flat panel display technologies, i.e., backlit double-supertwisted nematic liquid crystal display (LCD) devices, gas plasma devices, or electroluminescent displays, can compete in such areas as pixel contrast ratio and life, but only at the expense of uncomfortable viewing angle, slow response time, and low brightness.
Of the non-light-emitting displays, LCD displays are probably the most widely used. LCD displays use nematic liquid crystals operating on the principle that, when an electric field is applied, the direction parallel to the molecular axes becomes polarized to a different degree than the polarization in the perpendicular directions. Thus, light passing through the nematic layer is polarized as a function of the applied electric field. By sandwiching the nematic crystal layer between variously polarized layers, the light transmission through the sandwich can be controlled by the application of voltage to represent individual pixels.
LCD devices advantageously have very low power consumption and light weight. However, increasing the display contrast ratio and brightness requires double supertwist crystals and backlighting, both of which increase power consumption and add bulk. The main difficulty of LCD technology concerns pixel-addressing. Displays with conventional crossed-electrode addressing, with no active elements on each line, are limited in size because of the reduced ratio of on-voltage to off-voltage at a large number of scan lines. One alternative is to provide an active addressing scheme with thin-film transistors at each pixel. Thin-film transistors provide a memory characteristic to greatly increase contrast, but introduce substantial fabrication difficulties for large area devices.
These problems are addressed by the present invention, and an improved non-light-emitting flat panel display device is provided with increased brightness and contrast using only crossed-electrode addressing, and with memory capability for reduced power consumption. Accordingly, it is an object of the present invention to provide a flat panel display device that is non-light-emitting and can operate with passive addressing over a large area display.
It is another object of the present invention to provide a flat panel display device that requires only low power.
One other object of the present invention is a flat panel display device with gray level and color capabilities.
An object of the present invention is a flat panel display device with a high resolution display.
Still another object is a flat panel display that is light weight and compact.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.